There are several different types of layout tools that have been designed to assist carpenters in framing and construction of roof rafters, staircase stringers, spacing studs, marking rip lines, and the like. Carpenters often use framing squares for laying out staircase stringers and spacing studs. Perhaps the most famous tool for laying out roof rafters is the Swanson Speed Square offered by the Swanson Tool Co. of Frankfort, Ill. The speed square is shaped like a right-angle triangle with an enlarged lip or flange extending along one of the legs of the triangle.
The enlarged lip or flange of the speed square is a critical part of the speed square, for the speed square is positioned on a workpiece by pressing the speed square's lip against the workpiece straight edge. But the enlarged lip or flange makes the speed square, without an awkward accessory, unsuitable for laying out staircase stringers. Swanson Tool Co. offers a “Big 12 Speed Square” that combines an accessory that it refers to as a “layout bar” with a triangular speed square, for use in laying out staircase stringers. The layout bar, however, is not used to angularly align the speed square against a stringer. Rather, the layout bar simply adds a lip along the other “leg” of the right-angle triangle so that the speed square can be used to layout staircase stringers. Not only are two connectors required to connect the layout bar to the speed square, but also two separate “stop pegs” are required to configure the tool for laying out stringers. This particular product, in the inventor's opinion, is awkward, difficult, and time-consuming to use.